In short

Tips which cover the same material should be merged. Keep the first similar tip, and delete the others (after copying any useful material to the tip you are keeping).

Examples and explanations

Flag duplicate tips

Suppose you notice that tips 1 and 5 cover essentially the same material, but you're not currently able to take the time to merge the tips. In that case, you would flag each tip as being a Duplicate to alert readers that the tips need to be merged. That will also help someone reading one tip, because they will see that there is another tip covering similar material.